The invention concerns a multi-fuel injector for an internal combustion engine, a method for operating a multi-fuel injector and an internal combustion engine provided with a multi-fuel injector.
Multi-fuel injectors are typically used for carrying out combustion processes in combustion chambers of an internal combustion engine, wherein a not easily ignitable fuel is ignited by so-called ignition jets of an ignitable pilot fuel such as Diesel fuel. Multi-fuel injectors designed for combustion methods include a base body in which several nozzle needles are movably arranged, for example radially next to one another or also co-axially with regard to one another, wherein one of the nozzle needles may be hollow. Each of the different fuels is assigned its own nozzle needle and each nozzle needle is assigned a collection chamber disposed in front of the nozzle needle. The different fuels are injected separately by actuation of the respective assigned nozzle needles. Such multi-fuel injectors are complex in their design with several actuator sealing area and guide structures. Typically, the nozzle needles are hydraulically controlled wherein a control leakage needs to be carried away. It is noted that, whether a single multi-fuel injector or a plurality of injectors are used for performing a combustion process with different fuels, the hydraulic control of the various injectors or the different nozzle needles is performed always with the same fuel, in particular with the pilot fuel. The pilot fuel therefore comes necessarily also in contact with a conduit system for the other fuel or fuels, which is a problem. In particular, a permanent leakage at a control valve effective as a pilot valve has been found problematic since it is possible for the leakage fuel to enter the conduit system and particularly the reservoir for another fuel. It may occur for example that Diesel fuel enters a combustible gas rail and even a high-pressure storage area for the combustible gas or that combustible gas together with a pilot Diesel leakage enters a Diesel fuel tank. This results in problems during refueling of the tank and the fuel transport as it results in an increased explosion danger. In order to overcome these disadvantages, it would be necessary to develop additional safety features for the separation of the fuels.
It is the object of the present invention to provide a multi-fuel injector, a method for operating a multi-fuel injector and an internal combustion engine where the disadvantages mentioned above do not occur.